Mastering precise body motions to increase, efficiency, power, function and speed is important to gaining proficiency in a sport and for many types of rehabilitation. This mastery is often achieved by repetition. While repetition is important, it can be counter productive if the wrong motions are repeated. Therefore, it is important to make sure what is being repeated is the desired precise motion. Good coaching and use of training tools can be helpful to guide a sports competitor into proper motions for their sport.